It is well-known that surgical bioprosthetic heart valves are plagued with limited durability, with failure resulting from leaflet structural deterioration due to mechanical fatigue and/or tissue mineralization. Since the transcathete aortic valve (TAV) is made of similar biomaterials and acts as an alternative to a surgical bioprosthetic valve in the same anatomic position, we postulate that biomechanical damage also plays a major role in limiting TAV durability. Furthermore, due to the fact that the TAV has to be crimped into a small diameter catheter for valve delivery, design of a TAV is subjected to more constraints that may further impede its long-term durability. In this early, ye rapidly advancing stage of TAV development, we believe that identifying critical biomechanical factors that may lead to TAV device malfunction is of paramount importance, as it may result in the immediate improvement of the TAV design, prevention of disastrous device failure (due to high stress concentration, for example), and consequently better clinical outcomes for patients. In this project, our objective is to perform engineering structural analysis of transcatheter aortc valve devices, and compare with that of a clinically-proved surgical bioprosthetic valve to identify biomechanical factors that may cause TAV malfunction and offer mechanistic insights for TAV design improvement. To achieve our objective, the following specific aims are proposed: 1) quantification of TAV leaflet tissue mechanical properties; 2) development of TAV computational models with a variety of design variables. A novel valve virtual assembly method will be applied to construct 3D computational models of the TAV. The computational models will be validated by valve deformation experiments using physical TAV devices, 3) Engineering structural analysis of TAV deformation to identify biomechanical factors that may cause TAV malfunction. Project milestones are to: 1) establish databases of TAV leaflet tissue properties and TAV computational models; 2) identify TAV biomechanical damage factors and 3) at the conclusion, offer engineering rationale for a better TAV design.